The present invention relates to a method for preventing or suppressing resonance of piping caused by pulsation of pressurized fluid sent into the piping from a discharge pressure zone, which is intermittently supplied with the pressurized fluid.
Typically, an automotive air conditioning system includes a compressor. The compressor intermittently discharges compressed refrigerant gas (pressurized fluid) into a fluid passage, or piping, which is connected to the compressor. Therefore, pulsation occurs due to the flow of high refrigerant gas (or gas pressure fluctuation) in the piping. It is known that such pulses result in resonance, which produces noise. Accordingly, various proposals have been made to prevent resonance resulting from the pulsation.
Resonance may be prevented by modifying the structure of the fluid piping extending from the compressor so that the resonance frequency of the piping differs from the pulse frequency. For example, the hardness of the piping connected to the compressor may be changed. Alternatively, the length, weight, or degree of bending of the coupler that connects the piping to the compressor may be changed. In such cases, however, the resonance resulting from pulsation must be taken into consideration each time the piping is changed. This increases the production cost of the piping and decreases productivity.
Resonance may also be prevented when employing a multiple cylinder axial piston type compressor by forming some or all pistons, which are located in respective cylinder ores, with different lengths. In this case, the pistons having different lengths also have different top clearances, which is the clearance defined when the piston is moved to its top dead center position in the associated cylinder bore. This also changes the resonance frequency of the fluid passage from the pulse frequency and prevents resonance caused by pulsation.
However, the resonance frequency of the piping differs from one vehicle type to another. In other words, the piping of each vehicle type has a unique resonance frequency. Thus, the compressor must be modified in accordance with the vehicle type so that its pulse frequency differs from the resonance frequency of the piping. In other words, even if the same type of compressor is installed in different vehicle types, the top clearance of the pistons must be changed in accordance with the vehicle type. This increases in production costs and decreases productivity.